Question

While conducting reconnaissance, Greg discovers what he believes is an SMTP service running on an alternate port. What technique should he use to manually validate his guess?

A. Send an email via the open port.
B. Send an SMTP probe.
C. telnet to the port.
D. ssh to the port.

Answer 1

Greg should use telnet to connect to the suspected SMTP service running on an alternate port to validate his guess. If he is able to issue SMTP commands and sees appropriate responses, it confirms the existence of the SMTP service. The correct answer is C. telnet to the port.

Step-by-step explanation:

To manually validate his guess that an SMTP service is running on an alternate port, Greg should telnet to the port. By using telnet, he would be able to manually enter SMTP commands and assess the responses from the server.

This process can confirm if the service running on the port is indeed SMTP. If Greg receives an SMTP banner or is able to interact with the service using SMTP commands, he can be certain he has found the SMTP service on the alternate port.

Telnet is a network protocol that allows users to establish a secure remote connection to another device.

By using telnet to connect to the alternate port, Greg can test whether it is indeed an SMTP service by sending SMTP commands and observing the response.